Photographic emulsions containing sensitizing dyes



July 28, 1953 w. H. vlNToN ETAL I 2,647,051

PHOTOGRAPHIC EMULSIONS CONTAINING ,SENSITIZING DYES Filed Feb. 17, 1951 FIG.1.

Gelatin Silver lodobromide Emulsion Containing Dy'e Of ExampleI. I3:3'diethy| 5- carbomethoxy-S- methylthoselenacorbocyanine iodide) FISQt Gelatin Silver lodobromideEmulsion Containing Dye Of ExampleJI.

(3:3'- cliethyl -5- oarbomethoxy 5' chlorothiacarbocyanine ethosulfate) FI o 3,

/l-r` 3:0 360 400 44 450 520 550 $00 540 S80 720 /0 Gelatin Silver lodobromide'EmuIsion. Containing Dye Of Example El.

(3:3'-diethyl.5 carbomelhoxy -5' chlorothiaselenacarbocyanine ethosulfate) FIG.4.

INVENTORS WILLIAM HOWELLS VIN TON JOHN CHARLES FIRESTINE BY fynM/BM ATTORNEY Patented July 28, 1953 UNlrllov` STATES iPa-*rlt-lyrf.y t

PHOTOGRAPHIC EMULSIONS CONTAINING' f SENSITIZINGr` DYES William' Howells Vinton, Parlin, and John'GlarleS "l Firestine, South River, N.'J assignors to E. I. dunPont de Nemours & Company; Wilmington; Del., a corp'orationof Delaware Application February 17, 1951, Serial No. 211,583"

(Cl. 954-37)v Claims. l

This invention -is concerned with inewfunsymmetrical carbocyanine dyes. More particularly, it is concerned with unsymmetrical carbocyanine dyes which contain-va -carbalkoxybenzthiazole radical linked to a benzthiazole or benzselenazole radicalthrough a trimethineehain which may be unsubstituted or contain a hydrocarbon substituent on the central carbon atom of such chain. The invention also relates to photographic silver halide emulsions containing such carbocyanine dyes.

An object of this invention is to provide a new group of carbocyanine dyes. A further object is to provide a group of carbocyanine dyes which confer an eXtra range of sensitivity to a silver halide-emulsion in the red region of the spectrum. A further object of the invention is to provide such a group of carbocyanine dyes which do not have any significant sensitivity in the green region of the spectrum. Another object is to provide new colloid-silver halide emulsions which are green-blind. Still other objects Will be apparent from the following description of the invention.

The above objects are' obtained by the preparationl anduse of the unsymmetrical carbocyanine dye's of this invention which may be represented by theA generalforni'ula:

Where R is an alkyl radical, R' is an' alkyl radical of l to 4 carbon atoms, R" is a hydrogen atom oran alkyl radical of 1 to 3 carbon atoms, X is the negativeradical of an acid, Y is a chalcoge'n takenirom the group consisting of sulphur' and" selniumand Z is `a member taken from the group consisting of hydrogen, alkyl of 1 to 3 carbon atoms',l aryl of 4 to 10 carbon atorn's, chlorine andz bronnne and alkoiry of 1 to 3' carbon atoms.

Suitable specific radicals for R in the above formula include methyl, ethyl, n-propyl, iso` prpyl, benzyl gfor R include methyl, ethyl, rr'lpropyl, isopropyl and n-butyl, andfor RI" are methyl, ethyl, isopropyl, n-propyl. Suit'f'il'al'e` acid radicals represented by X are halogen; e. g.,-Cl;

Brand I; perchlorate, SCN, p-toluenesulfonate, methosulfate and ethosulfate.

Thedyes of Formula 1 can be' made byf con densing a Z-(beta-anilinol (or bet'aeacetanilinolvinyl-5-carbomethoxy benzotliiazole Quaternary salt with a Z-methylbenzothiazole ora 2-methylbenzoselenazole `quaternary salt in the" presence of an acid Ibinding agent,l e. "g., pyridine, dimethylamine, dethylamine, piperidine;/cyolohexylamine etc. andfheating the admxture under reux conditions.

trimetlgyldiii-ine,

amount of methanol.

PREPARATION'A .5J-'methyl-5-carbomethxybenzctltazol 'lo a solution of 6 0 g. of sodium hydosulfld 250 ml. of methanol there' was ad`ded8 fs'il i' fur, and the resulting solution was filtered' to move a small amount of insolublel n'late'zrial.VV "I'lie i resulting solution of sodium'y disuliide was added' dropwise over a period of'2.5 hours to a soldi" tion of 11o g. of methyl4-chloro-3-nitrdbedt in 250 m1. of methanol' heated to reflux; Th methyl 3-nitrobenzoate4dis`llide'" sepa `ted a solid during the addition of the 'sodium' disill-VJ nde. The mixture wascoled ,to dbdiit'e'or'o; ltered and the lter cake Washed Withla sliiavll The lte (fake 'Was'tlf stirred with warm Water't'o remove'thsodiiil chloride and air dried. This prdilt' Was'" duced with zinc dust and 'acetic' anhylidfa d? after distillation under reduced pressure- "P -165 C. at 1 mm.) was re'oiystalliz'ld f'ora'. mixture of benzene'and let'rfc'olel'izil` -etlei'to colorless crystals of Zmetlyl-cabtl' tenzothiazole melting at '9s-98' c.' *Indiadtidnvtakes place as followsl *C1 Nast CHaOOC -NOz PREPARATION n 2- (-dm'lz'no) vinyl-S-carbomethorybene'othzazole diethyl sulfate- CHaOOC fused-at 909 until it produced a solid-mass'.- The? .product was slurriedin alcohol and llteredo'. i

It Was then recrystallizedfrom alcohol using decolorizing carbon to remove impurites"."Thei"e The corresponding N-acetyl derivative can be formed readilyby the use of the same reactionv plus slightly greater than the theoretical amount of acetic anhydride.

The carbocyanine dyes of Formula 1 have been found to be quite useful photographic sensitizing dyes. When added to a colloid-silver halide emulsion they confer an extra range of sensitivity thereto in the red region of the spectrum with no substantial sensitivity in the green region of the spectrum. They constitute new greenblind" sensitizing dyes. These dyes have the additional advantage that iinished photographs are quite free from residual stain. The dyes are not limited in their use to any particular type of light-sensitive silver halide emulsion but they may be incorporated. in colloid-silver halide emulsions of various types including silver chloride, silver bromide, silver` chlorobromide, silver iodobromide, simple and mixed emulsions. Various types of water-permeable or hydrophilic colloids can be used as the binding agents for the light-sensitive silver halide grains, e. g., gelatin, albumin, agar agar; hydrophilic cellulose acetate, polyamides, hydrolyzed ethylene/vinyl acetate copolymers; polyvinyl alcohol, polyvinyl acetals, etc., hydrophilic colloid color formers, e. g., polyvinyl acetals of color-forming aldehydes.

The preparation of representative unsymmetrical carbocyanine dyes of this invention will now be described in the following examples.

Graphs of spectrograms of gelatin silver halide emulsions containing the respective dyes of the following examples are shown in the accompanying drawing, wherein,

Fig. 1 is a spectrogram of the dye of Example I in a gelatin silver iodobromide emulsion,

Fig. 2 4is a `spectrogram of the dye of Example II in a gelatin silver iodobromide emulsion,

Fig. 3 is a spectrogram of the dye of Example III in a` gelatin silver iodobromide emulsion, and

Fig. 4 is a spectrogram of the dye of Example IV in a gelatin silver iodobromide emulsion.

EXAMPLE I Preparation ofdye of the formula:

oHsoc CH3 l N N C515 I CzHs In a suitable reaction vessel there were placed 2.32 g. 2-(beta-anlino)vinyl-5-carbomethoxybenzothiazole ethyl ethosulfate, 1.83 g. of 2,5-dimethylbenzoselenazole ethiodide, 20 ml. of dry pyridine and 5 ml. of acetic anhydride. The mixture was heated under conditions of reflux for ve minutes. A deep purple color formed and the dye crystallized out of solution. The dye was filtered oil", washed with water and then recrystallized twice with ethyl alcohol. The sparkling green crystals of the dye (3:3-diethyl5-carbomethoxy 5' methylthiaselenacarbocyanine iodide) of the above formula which were obtained had a melting point of 254 to 255 C. An ethanol solution of the dye had an absorption maximum at 568 millimicrons.

A small amount of the dye was added to a gelatine silver iodobromide emulsion of the negative type andwas found to confer an extra range ofv sensitivity to such emulsion extending from 550 millmicrons to 672 millimicrons. Y

EXAMPLE II Preparation of the dye of the formula:

In a suitable heat-resisting glass flask there were placed 1.83 g. of Z-methyl--chlorobenzothiazole and 1.54 g. of diethyl sulfate. The mixture was heated for two hours at 12o-130 C. and then 4.18 g. of Z-(beta-anilino)vinyl--carbomethoxybenzothiazole ethyl ethosulfate and 20 ml. of dry pyridine were added. The mixture was heated to reflux for 30 minutes and a brilliant purple color` formed and the dye crystallized out of solution. The dye (3:3'-diethyl5-carbo- 1nethoxy-5'-chlorothiacarbocyanine ethosulfate) which had the above formula was filtered, washed, recrystallized several times from ethyl alcohol whereupon sparkling purple crystals of the dye having a melting point of 26S-267 C. were obtained.

An ethanol solution of this dye showed an absorption maximum. at 560 millimicrons. When a small amount o1" the dye was added to a gelatine iodobromide emulsion of the negative type, it was found to extend its sensitivity to 660 millimicrons with a maximum at 640 millimicrons.

When a small amount of the dye was added to a gelatino silver bromochlorlde emulsion of the lithographie type it extended the sensitivity from 53C to 621 millimicrons with a maximum at 596 mi limicrons. The emulsion evidenced little sensitivity in the green region of the spectrum.

EXAMPLE III Preparation of dye of the formula:

CHaOOC In a suitable heat-resisting glass flask there was placed 1.15 g. of Z-methyl-B-chlorobenzoselenazole and 0.77 g. of diethyl sulfate. The mixture was heated for two hours at -130 C. and 2.32 g. of 2-(beta-anilino)vinyl--carbomethoxybenzothiazole ethyl ethosulfate and 20 ml. of dry pyridine were then added and the mixture was heated under reuxed conditions for 30 minutes. A deep purple color formed and the dye crystallized out on cooling. The dye (3 3 -diethyl-5-carbomethoXy-Ei chlorothiaselenacarbocyanine ethosulfate) which had the above formula was ltered off, washed With water, and recrystallized twice from ethyl alcohol. The sparkling purple crystals of this dye had a melting point of 275-277 C.

An ethanol solution of the dye showed an absorption maximum at 6170 units. A small amount of the dye was added to a gelatino iodobromide emulsion of the negative type and was found to extend its sensitivity to 660 millim'icrons with a maximum at 640 millimicrons.

EXAMPLE IV S S oclH.

. demon-omo cmo- \N/ In a suitable flask there were placed 2.45 grams 2-methyl-6-ethoxybenzothiazole ethiodide, 2.32 grams 2(betaanilinovinyl) -5-carbomethoXybenzothiazole ethyl ethosulfate, 2O ml. dry pyridine and ml. of acetic anhydride. The mixture was heated to reflux for 5 minutes and a purple color formed. On cooling the dye precipitated out of solution. The dye Was filtered off, washed with ethyl alcohol and recrystallized twice from ethyl alcohol. A yield of 1.14 g. of purple dye was obtained which melted at 257-258 C. An ethanol solution of the dye showed an absorption maximum at 562 millimicrons. A small amount of the dye (3:3'-diethyl-5-carbomethoxy-6-ethoxythiaearbocyanine iodide) was added to a gelatino silver iodobromide emulsion and extended the sensitivity to 630 millimicrons with a sensitivity maxmum at 600 millimicrons. The emulsion evidenced substantially no sensitivity in the green region of the spectrum.

Various other unsymmetrical carbocyanine dyes containing diierent alkyl halide or ester radicals than those described in the foregoing examples can be made in a similar manner by substituting for the diethyl sulfate other alkyl salts such as ethyl p-toluenesulfonate, methyl ptoluenesulfcnate, ethyl iodide, methyl chloride and ethyl benzenesulfonate.

The ethyl ethosulfate quaternary salts of the foregoing example can be converted into the quaternary salt by a metathetical reaction, e. g., into the corresponding bromide or iodide by the addition of sodium iodide, potassium bromide, ammonium chloride; potassium thiocyanate, etc.

Similarly, in place of the 2-(betaani1ino) vinyl-5carbomethoxybenzothiazole diethyl ethosulfate there may be substituted other carbalkoxybenzothiazole derivatives, e. g., the corresponding carbethoxy, carbo-n-propoxy and carbon-butoxy, carbo-tertiary butoXy, etc.

In place of the 2-methyl--chlorobenzothiazole, 2-methyl-5-chlorobenzoselenazole and 2,5-dimethylbenzoselenazole there may be substituted other benzthiazoles or benzselenazoles which contain a substituent having the value Z in Formula 1. Among the useful reactants are 2- methyl--ethoxybenzothiazola 2 methylbenzoselenazole, 2-methyl-4- (beta-benzothiophene) thiazole, 2,5-dimethylbenzothiazole, 2-methyl-5- bromobenzothiazole, 2-methyl-5-bromobenzose- I lenazole, 2-methyl-5-propoxy-benzoselenazole, 2- methyl-5-phenylbenzothiazole An advantage of this invention is that it provides the art with a new group of sensitizing dyes. These dyes are of considerable importance in color photography because they do not confer any signicant sensitivity in the green region of the spectrum. They are also non-migratory and thus advantageous in multi-layer color photographic elements.

As many widely dilTerent embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as dened by the claims.

What is claimed is:

1. A Water-permeable colloid silver halide emulsion layer containing a compound having the general formula:

Where R is an alkyl radical, R' is an alkyl radical of 1 to 4 carbon atoms, R" is a member taken from the group consisting of hydrogen and alkyl radicals of 1 to 3 carbon atoms, X is the negative radical of an acid, Y is a chalcogen taken from the group consisting of S and Se and Z is a member taken from the group consisting of hydrogen, alkyl of 1 to 3 carbon atoms, aryl of 6 to 10 carbon atoms, chlorine, bromine and alkoxy of 1 to 3 carbon atoms.

2. A gelatine silver halide emulsion containing a compound having the general formula:

Where R is an alkyl radical, R' is an alkyl radical of 1 to 4 carbon atoms, R" is a member taken from the group consisting of hydrogen and alkyl radicals of 1 to 3 carbon atoms, X is the negative radical of an acid, Y is a chalcogen taken from the group consisting of S and Se and Z is a member taken from the group consisting of hydrogen,

alkyl of 1 to 3 carbon atoms, aryl of 6 to 10 carbon atoms, chlorine, bromine and alkoxy of 1 to 3 carbon atoms.

3. A water-permeable colloid silver halide emulsion containing the compound of the formula:

S Se \C- cH=CH-CH= l 4. water-permeable colloid silver halide emulsion containing the compound of the formula:

5. Water-permeable colloid silver halide emulsion containing the compound of the formu a:

WILLIAM HOWELIS VINTON. JOHN CHARLES FIRESTINE.

References Cited in the le 0f this patent UNITED STATES PATENTS 

1. A W ATER-PERMEABLE COLLOID SILVER HALIDE EMULSION LAYER CONTAINING A COMPOUND HAVING THE GENERAL FORMULA: 